Field of the Invention
The present invention relates to a novel foam excellent in mechanical properties and heat-resistance and having a good appearance. More particularly, the invention relates to a high-performance foam having a uniform and closed cell structure and a smooth appearance, provided with mechanical characteristics and heat resistance which have never been obtained and having a high reliability for a long period of time, the foam being composed of a substantially non-crosslinked polyethylene having a density of 0.935 g/cm.sup.3 or more and a melting point of 117.degree. C. or more.